A homeowner asked me to take a look at a Lithonia wall pack (TWS) that wasn't working. This light, mounted at the back of the house, is used as a security light for a rather dark and hidden area of the backyard. Even before I attempted to determine the reason the light no longer worked the homeowner made it obvious they would prefer a LED light instead of the 70W HPS. When I asked why the owner replied that they felt it ran too hot which caused the lens to warp (I didn't see the lens since they had it removed before I arrived). After looking at the way the fixture was installed, horizontally instead of vertically due to variations in the siding and conduit running out the bottom KO to a remote photo eye, I thought the simplest fix would be to retrofit the fixture with a suitable LED bulb. I called a local supplier with the details and was a little surprised when they quoted me $125 CDN for a 18W LED (2160 Lumen and 4000K). Another option was to buy a Lithonia TWS LED wall pack for a few dollars more although it is only rated for a 1000 Lumen. I then inquired about a $25 18W LED (Cree brand, 2160 Lumen, and 4000K) and what the difference was between it and the $125 model. The sales rep said it had to do with "optics" and that in the right fixture it would have more "punch"...? I do not know what brand the $125 LED bulb was but I do know that it is meant to replace a Metal Halide or HPS and that physically it is different in appearance than the cheaper incandescent looking LED. Other than that does anybody know if there is a significant difference in light output and light quality between these equally rated but substantially different in price LED bulbs?

A malfunction at the junction--------------------------------------Dwayne

Sparky, I wonder if that lamp would even fit in the old Lithonia wall pack fixture? The sales rep I spoke with brought the subject up that it may be a little tight and asked me if the original HPS had a good amount of open space around it. Tough call without ever seeing the LED up close.

A malfunction at the junction--------------------------------------Dwayne

sparkys nice retro more than likely will not fit in the existing wallpack.

The 18/100 Cree may not provide the illumination of the area in the clients 'eye', even though it's 'white light' as opposed to the yellow/orange of the HPS. That is unless they had the 'white HPS' that is pricey.

As you mentioned, the lens is 'warped', per the client; I would strongly suggest they buy a new complete fixture.

I think your 18 watt LED bulb in a HPS (or MH) fixture will produce a lot less light.

HPS and LED produce about the same number of lumens per watt. To get the same amount of light from an LED as a 70 watt HPS, the same amount of heat is created. An LED can't survive that in an enclosed fixture.

The LED is different because it's very directional. This allows you to use a fixture that puts all the light where it's needed and almost none where it isn't needed. The reduction in waste means fewer lumens and watts are needed.

A fixture made for an LED will have heat sinks and might aim the light produced in one direction. Depending on how much light spread you need, you might choose an LED or HPS.

Went to the house today and removed the ballast from the Lithonia wall pack. I went ahead and installed the Cree 18W LED. The lens was not warped as I thought I had been told. It had a dark spot on the side of the lens that was facing up (remember, it was installed on the horizontal).

twh, concerning your comment about the heat affecting the LED in an enclosed fixture - I was talking to another electrician today about that very subject. Likely another reason the other LED bulb recommended for this type of retrofit is so much more expensive. It likely has some built in heat dissipation when used in an older fixture. Although the Lithonia wall pack has a gasket around the edge of the lens it doesn't close tight around the KO. The lens isn't damaged so it's just the way it's designed. The way the fixture was mounted this opening is on one side and may allow for some heat to escape. The fixture faces south but sits in a corner of the house with tall trees in front so I doubt it sees much direct sun. Definitely not a perfect solution but if it lasts a good number of years then it will be the most economical.

BTW, the Cree 18W LED just fit in this fixture. Length wasn't a problem but it sits right against the reflector. I didn't have to force it in but there's no room to spare on that side.

A malfunction at the junction--------------------------------------Dwayne

Went out for supper this evening and ended up not far from the house where I did the work. Drove by on the way home to take a look at how bright the light was. Even though it wasn't fully dark outside that light seemed really bright and my wife and I were looking from a fair distance away. If the main goal was to attempt to deter thieves from breaking into the house by entering the basement window in that corner then this retro-fit was a success. Other than discovering that the LED has a short lifespan in that fixture I would not hesitate to retro a fixture in the same manner again.

A malfunction at the junction--------------------------------------Dwayne